Abstract:This paper outlines a completely deterministic ('constructual') theory of why quasi-similar street patterns exist, how they form, and how they grow in time. The function of the street network is to connect a finite area to a single destination point. The new idea is that the network of streets evolves in time, by starting with the optimization of the shape of the smallest area element that is serviced by the network. Next, the optimized area elements are assembled into a larger area element which is again optimized for shape. This sequence of optimization & organization is repeated in finite-size steps, toward larger quasi-similar assemblies. The optimization consists of minimizing the travel time between each point of a finite area and a common point of destination. The network is constructed (optimized, organized) in time. Every single geometric feature of the network is the result of pure, deterministic theory: the shape of each area element, the shape of each new (larger) assembly, the optimal number of parts in each assembly, the relative orientation of successive streets, and the optimal width of each street.